Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$204.44	9.605%	$224.0765	$224.08	$224.10	$224.10
Purchase #2	$39.91	6.569%	$42.5317	$42.53	$42.55	$42.50
Purchase #3	$154.37	8.595%	$167.6381	$167.64	$167.65	$167.60
Purchase #4	$158.29	13.792%	$180.1214	$180.12	$180.10	$180.10
Purchase #5	$99.36	13.271%	$112.5461	$112.55	$112.55	$112.50
Purchase #6	$146.88	4.829%	$153.9728	$153.97	$153.95	$154.00
Purchase #7	$136.72	11.404%	$152.3115	$152.31	$152.30	$152.30
7 purchase totals =	$939.97		$1,033.1981	$1,033.20	$1,033.20	$1,033.10